1) Field of the Invention
The present invention relates to an antiglare material used on an image display such as LCDs, CRTs and the like to exhibit an excellent antiglare effect on the displayed images as well as to a polarizing film by the use thereof.
2) Description of the Related Art
It is a very common technological practice under rapid progress in recent years that various kinds of image display devices, referred to simply as "displays" hereinafter, including LCDs and CRTs as typical examples are widely employed in a variety of fields for the exhibition of images and patterns as in television sets, computer terminals and the like. While one of the key problems in the initial stage of their development was to accomplish conversion of the black-and-white displays into colored displays, it is a recent trend in the development works to accomplish upgrading of the image quality of the displays with higher and higher resolution as represented by the movement toward the new television broadcasting system of increased image resolution in addition to a further target of the development works to accomplish saving of the electric power consumption in the displays. These innovative display systems are expected to play a very important role in the man-machine interphases with wider and wider prevalence along with the advent of the era of so-called multimedia including, in particular, a variety of portable terminals of communication systems represented by portable telephones, PHS, and the like.
It would be a due expectation that LCDs are the only displays which occupy the market of the displays for portable terminals since they are the lightest in weight and can be designed with compactness along with their versatility for any types of displays. Since these portable terminals are frequently used outdoors, it is important to ensure good visibility of the images exhibited on the display screen even under daylight by suppressing reflection of the external light incident on the display screen such as the sunlight as completely as possible. As being urged by the requirement in these fields, it is eagerly desired to develop an efficient antiglare means on the display screen which prevents imaging reflection of external light sources such as the sun, fluorescent lamps and the like on the display screens.
The most conventional way in the prior art to accomplish the antiglare effect of this type is to use a glass plate having a ground or matted surface and the like by which the incident light is scattered or diffused to exhibit a vignetting effect on the images. The scattering or diffusing effect on the light is accomplished usually when the surface for the incident light is matted or roughened as a basic principle. Several different methods are undertaken for the roughening treatment of a substrate surface including the direct roughening methods such as sandblasting, embossing treatment and coating treatment by which a coating film containing fine filler particles dispersed therein is formed on the substrate surface as well as a method in which a surface layer having porosity by way of the so-called "sea-and-islands" structure is formed on the substrate surface.
While a high degree of resolution of the image display can be accomplished mainly by increasing the distribution density of the image-forming dots, increase of the distribution density of the image-forming dots is necessarily accompanied by an increase in the fineness of the height difference of and distance between the irregularity protrusions on the roughened surface. Further, sharp display images without glittering cannot be obtained unless the evenness in the distribution of the surface irregularities is minimized. In addition, a good antiglare effect can be obtained when the surface irregularity is formed with continuity or without intermission. The roughened surface of conventional antiglare materials, however, does not always satisfy the above mentioned various requirements in respects of the discontinuity in the distribution of the surface irregularities and relatively large height of and distance between the raised points of irregularity on the substrate surface.